CVE-2026-53512
Last modified
CVE-2026-53512 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. EPSS estimates a 0.30% chance of exploitation in the next 30 days.
Description
Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. The @better-auth/oauth-provider package is not affected. This issue is fixed in version 1.6.11.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Better-Auth | Better Auth | < 1.6.11 |
References
- https://github.com/better-auth/better-auth/pull/9576Issue Tracking, Patch
- https://github.com/better-auth/better-auth/security/advisories/GHSA-pw9m-5jxm-xr6hMitigation, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
Frequently Asked Questions
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How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Uncovering a hidden BOLA in Appsmith's snapshot logicStrix autonomously discovered a BOLA/IDOR vulnerability in Appsmith's snapshot deletion path.
- Same Subject, Wrong User: A Cross-Issuer Account Takeover in n8nStrix found an identity-binding bug in n8n's token-exchange flow enabling account takeover.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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